The benefit of producing lumber from curved cants by cutting the cants along a curved cutting line, as dictated by the configuration of the cants, is well known to the industry. One way of accomplishing such curved cutting is by feeding the cants in a linear path to the saws and manipulating the saws rotatively and laterally to follow a projected curved cutting line through the cant. It is this cutting process to which the present invention is directed.
The required movements of the saw, i.e., laterally and rotatively, has heretofore required a carriage for the saw that is movably mounted on a base member, e.g., rotatively, with that base member movably mounted, e.g., laterally, on a second but fixed base member. The provision of such dual movement on dual base members is both complex and expensive. It is an objective of this invention to produce the desired dual movements on a single fixed base member.
Determining the optimum positioning of the saw is also an objective of this invention. The saw that is used for cutting is a bank of planar circular saw blades. The portion of the circular periphery of the rotating saw blade that cuts the cant is angled upwardly and rearwardly and is substantially a straight inclined cutting edge. FIG. 6 illustrates the cutting of a cant by a circular saw blade and the portion referred to as the inclined cutting edge portion is between points 104 and 102. This cutting edge portion has both length and height and the length portion is straight whereas the projected kerf being cut by the blade is curved. Thus the blade is constantly repositioned to follow the kerf and because the blade is straight and the kerf is curved, only a single point on the cutting edge portion of the blade can be truly on the projected kerf. This point is referred to as the point of tangency. The effect on the lumber being cut is that the sawn side of an outside or face board is not flat and thus not parallel to the chipped outer flat side produced by a chipper. (Chipper cutting occurs along a vertical line and thus produces a flat face regardless of alignment.)
In known prior devices, the closely adjacent but necessarily spaced apart saw and chipper are commonly mounted for simultaneous positioning, laterally and pivotally. Any change to the assembly affects both the chipper and the saw blade, and the point of tangency (determined by the pivot point for the assembly) is established rearward of the chipper and forward of the saw.
Neither the chipper or the cutting blade is precisely positioned on the projected kerf and the sawn side is not only not flat but it is non-symmetrical which can affect the grading of the lumber.